Unfortunately, there is no easy way to do this. The list of months is generated dynamically when the reports are run.
If you are familiar with HTML, something you could do is modify the select statement in the template titlebar.inc to include the extra dates. For example, say you had extra months 2010-08 and 2010-09, contained in files NOAA/NOAA-2010-08.txt and NOAA/NOAA-2010-09.txt, respectively. When done, this would look like (NOT TESTED):
<select name="reports" onchange="openTabularFile(value)">
<option value="2010-08">2010-08</option>
<option value="2010-09">2010-09</option>
#for $monthYear in $SummaryByMonth
<option value="$monthYear">$monthYear</option>
#end for
<option selected>- $gettext("select month") -</option>
</select>
This would make the extra dates available in the drop down list.